On Thu, 13 Apr 2023 at 16:14, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > Hi Marco, > > On Fri, Feb 24, 2023 at 09:59:39AM +0100, Marco Elver wrote: > > Clang 15 provides an option to prefix memcpy/memset/memmove calls with > > __asan_/__hwasan_ in instrumented functions: https://reviews.llvm.org/D122724 > > > > GCC will add support in future: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777 > > > > Use it to regain KASAN instrumentation of memcpy/memset/memmove on > > architectures that require noinstr to be really free from instrumented > > mem*() functions (all GENERIC_ENTRY architectures). > > > > Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions") > > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> > > Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > > Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> > > Tested-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx> > > Tested-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> > [...] > > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan > > index b9e94c5e7097..fa9f836f8039 100644 > > --- a/scripts/Makefile.kasan > > +++ b/scripts/Makefile.kasan > > @@ -38,6 +38,11 @@ endif > > > > CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable)) > > > > +# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*() > > +# instead. With compilers that don't support this option, compiler-inserted > > +# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures. > > +CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1) > > + > > endif # CONFIG_KASAN_GENERIC > > > > ifdef CONFIG_KASAN_SW_TAGS > > @@ -54,6 +59,9 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \ > > $(call cc-param,hwasan-inline-all-checks=0) \ > > $(instrumentation_flags) > > > > +# Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*(). > > +CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1) > > This patch breaks the arm64 kernel builds with KASAN_SW_TAGS enabled and > clang prior to version 15. Those prior clang versions don't like the > '-mllvm -hwasan-kernel-mem-intrinsic-prefix=1' option, end up printing > the help text instead of generating the object. > > Do we need some combination of cc-option and cc-param? Or at least > disable this instrumentation if earlier clang versions are used. > > It's already in mainline as commit > 51287dcb00cc715c27bf6a6b4dbd431621c5b65a. Arnd posted a patch, but the reason why a workaround is needed is quite unfortunate: https://lore.kernel.org/all/CANpmjNMwYosrvqh4ogDO8rgn+SeDHM2b-shD21wTypm_6MMe=g@xxxxxxxxxxxxxx/ Clang apparently interprets unknown options that start with "-h..", i.e. "-mllvm -h..." as a request to print help text, which has exit code 0. So this is only a problem for hwasan options.
